Nine burned Cedar Creek plots showed 24% biomass composition recovery and 48% richness recovery relative to controls, 2015–2022

We tested whether plant richness and biomass composition showed the same recovery after nutrient addition stopped at Cedar Creek, Minnesota. We used nine burned plots at the three highest addition rates, 9.52–27.2 g nitrogen per square metre per year, with other nutrients. After 32 years of addition, each plot had one stopped half and one continued half. We compared both halves with three same-year unamended controls in six sample years from 2015 to 2022. Richness recovery was the fraction of the control deficit removed. Composition recovery was the fraction of excess Hellinger distance above control-to-control distance removed. Stopped halves showed 48.1% richness recovery and 24.1% recovery in relative biomass composition. The mean distance improvement was 0.133, with a 95% treatment-plot bootstrap interval of 0.097–0.170, conditional on controls and years. All nine plot effects were positive. The Holm-adjusted sign-flip p-value was 0.0117, assuming exchangeable half assignment. Bray–Curtis distance gave 22.7% composition recovery. Equal weights for present taxa gave 46.6%. Omitting individual controls gave biomass recovery of 21.8–25.6%. Recovery increased over time: the final two sample years gave 44.3% biomass recovery and 63.0% richness recovery. These results extend an earlier SCI richness study. The general difference between richness and abundance recovery is already known. The result is limited to the stated metrics, plots, and current controls. Side assignment is documented directly for unburned field C but remains an assumption for field B. The package has source data, provenance, code, figures, and a clean reproduction check.

grassland · nutrient enrichment · ecological recovery · species composition · Cedar Creek · Hellinger distance · open data